This invention relates to a process for the regeneration of a scrubbing medium which has been utilized in a pressurized scrubbing operation and therein loaded with scrubbed-out components, this scrubbing medium being expanded, regenerated, and then reused in the scrubbing operation.
In scrubbing operations, throttle valves are usually employed for expanding the loaded scrubbing medium from the scrubbing column to a lower pressure. Expansion turbines are utilized only in cases where large liquid quantities are involved for purposes of energy recovery. The use of expansion turbines, in spite of energy recovery, has several drawbacks.
The cost of turbines is very high so that they are economical only if the amount of recoverable energy is potentially large.
If the loaded scrubbing medium is extensively degasified, difficulties are encountered in the turbine due to an unfavorable liquid/gas volume ratio. On account of the fact that expansion turbines are prone to trouble, it is necessary either to insert a second unit in parallel as a standby or to install a throttle valve.
If an expansion turbine is coupled with the scrubbing medium pump, a motor must also be connected to the pump to provide make-up pump energy as required, and in order to provide the entire pump energy in case of failure of the turbine or during startup of the plant.
Based on the aforementioned disadvantages, it is customary, for example in acid gas scrubbing operations, to utilize expansion turbines only in large installations (i.e., in case of liquid quantities of several 100 m.sup.3 /h) and with relatively large pressure drops. On the other hand, there is interest in providing for gas compression in many scrubbing operations--especially in physical scrubbing processes for acid gas removal--wherein the liquid quantities or pressure drops do not justify the employment of an expensive turbine. For example, gas compression becomes of interest when expansion gases are to be recycled into the crude gas or utilized as a product for further treatment or when the scrubbing medium is to be subjected to a vacuum in order to lower the gas load in the expanded scrubbing medium.
Customarily, compressors are utilized for such compression needs. Besides the energy consumed for compression, an additional disadvantage associated with the employment of compressors is that the gas is heated in the compressor. For this reason, in most cases a recooler is also required for recooling the compressed gas. If the compressed gas is to be further treated in the scrubbing operation, which is very often the case, especially with H.sub.2 S-containing gases, refrigeration losses are imposed by this compression, and these losses must be covered by external refrigeration.
Therefore, East German Pat. No. 119,610 teaches one to effect compression of expansion gases, obtained under vacuum, by means of a jet comressor, also called a jet ejector. In this process, gases obtained during an intermediate expansion, which have a higher pressure than the gases to be compressed, are utilized as the propulsion media for the jet compressor.
The essential advantage of this process resides in that no external energy is needed for compression, and, at the same time, there is no heating for the exhausted expansion gases. However, the method can only be employed if a relatively large amount of expansion gas, at a higher pressure, is already available and, at the same time, if all gases can be discharged without being under pressure. A further drawback involved is the additional installation of expansion tanks which serve for obtaining propulsion gases for the jet compressors.